"He has made no decision on the nuclear deal, whether to stay in or get out," Bolton told Fox News Sunday.

"He is certainly considering the framework, the four pillars that President (Emmanuel) Macron laid out in their meeting last week," said Bolton, referring to efforts to supplement the Iran deal with additional measures to make it more palatable to Trump.

In 2015 the United States, along with other nations, struck a deal with Iran to end a 12-year standoff over that country's nuclear program, which was feared to be leading towards an atomic weapons capability.

Iran agreed to freeze its nuclear program in return for the lifting of punishing international sanctions, but Trump has criticized the deal as not going far enough.

Britain, France and Germany -- the three European countries that signed the Iran nuclear deal -- are working to head off Trump's threat to walk away from the accord and reimpose sanctions.

Trump has called the existing accord "insane" and "ridiculous," in part because its restrictions start to expire in 2025.

French President Emmanuel Macron has proposed an additional deal that extends Iran's nuclear restrictions while also curbing its ballistic missile program and support for militias in the Middle East.

Iran's President Hassan Rouhani rejected any hopes of rewriting the nuclear deal itself.